1. Field of the Invention
The Present invention relates generally to the art of semiconductor manufacturing and, more particularly, to an apparatus and method for identifying wafers contained inside a process tool chamber.
2. Description of the Relevant Art
Particle contamination of wafers is a serious problem in semiconductor manufacturing. During manufacturing, unprotected wafers may be exposed to airborne particles particularly when the wafers are transported from one process tool to another. Often times, these particles land on the surface of an unprotected wafer and create shorts or other performance degrading deformities in the underlying semiconductor device. Accordingly, it becomes important to avoid exposing wafers to foreign particles.
Semiconductors are manufactured in clean room environments which employ sophisticated filter systems to remove a significant amount of airborne particle contaminates. In particular, the filter systems provide a constant air flow vertically directed from ceiling to floor. Micro filters placed at the beginning of the air flow trap minute particles before they enter the clean room. The air flow ends at the clean room floor where air is recirculated back to the ceiling and filter system. Although the filters remove a significant amount of contaminates from the clean room, particles remain which may cause wafer contamination.
Semiconductor manufacturing involves a succession of processing steps whereby silicon wafers are transformed into integrated circuits. Each process step usually involves using one of several different types of process tools, including ion implanters, etchers, etc., each of which is usually contained in the clean room. Between process steps, wafers in cassettes are physically moved from one tool to another. During transfer, the wafers are tracked to ensure that they are directed to the proper process tool for subsequent processing. Prior to the present invention, cassettes of wafers were tracked using a hand-held bar code scanner (not shown). A clean room worker typically would remove a cassette from one process tool, and physically transport a cassette to a subsequent process tool for further processing. Before loading the cassette into the subsequent processing tool, the clean room worker scans a bar code displayed on a side of the cassette which contains identification information of the wafers therein in order to verify the next processing step. Often times due to simple oversight the wrong cassette is loaded into the process tool after scanning thereby resulting in wafer misprocessing. Further, movement of the hand-held bar code scanner disrupts particles resting thereon causing them to become airborne thus creating an enhanced risk that exposed wafers will be contaminated.